I can’t see the use case for pointing from a Wix subdomain to your 1&1 domain / WordPress installation. I think I misunderstood your initial question because of that, sorry. In this case you shouldn’t change your 1&1 nameservers into Wix. So you might reset this setting and test it again with a CNAME entry at Wix and with the default 1&1 nameservers on our side.

Please help i am unable to setup my core php base app. i am unable to figure out in which folder do i need to upload my website before installing and how it will be displayed.
I am using filezilla
if any body have relevant video please share.

if you downloaded your application from somewhere, it should already have a main folder and files. You can upload these with FileZilla on your webspace using SFTP. Afterwards you connect your domain with the main folder of the application.

My main domain is linked to other name servers not 1&1 and in the same time I want to link one of the subdomains to another name server, It is possible?
I tried but find hat if I point my main domain to other name servers than 1&1 as DNS1 I can not point the subdomain to another one as DNS2.
I am write or there is some thing i missed.

as soon as you are using an external nameserver for the main domain, the configuration of the subdomains can only be handled on this external nameserver system. So you have to go to this provider and change the settings for the subdomain on their systems.

generally you have to add our MX Records into the Wix system. In your case it looks like this was already done. The dns settings look good now and you should be able to use our mail services like you were used to all the time. 🙂